The present invention relates to cemented carbide bodies and particularly to cemented carbide bodies with a nickel binder in lieu of cobalt that have been treated with boron.
The cutting and drilling industries continue to place increased demands on cutting implements to hold a sharper edge and to last longer. Ordinary cemented carbide-tipped cutting elements consist of a mixture of tungsten carbide (WC) as a hard metal phase and Cobalt (Co) or Nickel (Ni) as the primary constituent of a binder phase. WC and Co powders are sintered to create a WC/Co cemented carbide body. Sometimes Nickel is used in lieu of Cobalt as the binder phase former, to form a WC/Ni cemented carbide body. As is known in the art, many modifications have been made to the simple WC/Co body to enhance its properties for various applications. In general, there is a trade-off between brittleness and hardness. If a harder metal is chosen to cut better and hold a sharper edge, it tends to be more brittle and therefore to suffer brittle failure sooner than a material that is not as hard.
To avoid the problem of increased brittleness while still improving hardness, some people have provided a boron addition as a thin surface coating or layer onto the carbide body. The surface coating or layer may be applied by thermal spraying, physical vapor deposition, chemical vapor deposition, and other known methods. It is also known to diffuse boron into the surface of the cemented carbide body to form a thin, hard layer.
A major problem inherent in all of the attempts to provide a boride coating or layer on WC/Co, WC/Ni or other carbide bodies is that, once the thin surface has been worn away, the hardness and other improved features are lost and the tool can no longer be used satisfactorily. If coated saw tips are first brazed onto a saw blade and then sharpened in place, the coating or surface layer may be lost due to the initial sharpening. It would almost certainly be lost on subsequent sharpening. Other problems include the fact that the layer has different thermal expansion and other properties than the substrate and therefore may tend to separate from the substrate during use. Brazing of pieces with layers or coatings is also difficult.